Cream butter and cheese, Blend in egg yolk and vanilla, Add cake mix 1/3 at a time; mix well, If mixer is used, add last part of cake mix by hand, Chill dough 1/2 hour, Heat oven to 375° (quick moderate), Drop by scant teaspoonfuls on ungreased baking sheet, Bake 8 to 10 minutes until delicately browned,______, Makes 6 to 8 dozen cookies,